Easy. Install imagemagick:
sudo apt-get install imagemagick
It's simplest usage is:
convert File.tif File.jpg
It is smart and goes by your file extension.
Now, for doing batch conversions, we shall use a loop.
cd into the directory where your tif files are.
for f in *.tif; do echo "Converting $f"; convert "$f" "$(basename "$f" .tif).jpg"; done
That should do it!
Also, once you convert all of the files and verify the new jpg's integrity, just run
rm *.tif in that directory to delete all your old .tif files. Be careful with asterisks though, don't add a space after the
*, or you will delete all your files in the directory.
Tip: If you have a folder with subfolders that holds these images. You could use this for loop to find all .TIF files within that folder:
for f in $(find -name *.tif); do ...; done